Which of the following is a major component of the endocrine system?

The pituitary gland is a significant part of the endocrine system because it serves as a master regulator of hormone production in the body. It is often referred to as the "master gland" because it controls other endocrine glands and influences a variety of bodily functions, including growth, metabolism, and reproduction. The hormones secreted by the pituitary gland, such as growth hormone, thyroid-stimulating hormone, and adrenocorticotropic hormone, play critical roles in regulating physiological processes.

In contrast, while the kidney, liver, and lungs perform essential functions in the body, they are not primarily classified as components of the endocrine system. The kidneys are involved in filtering blood and regulating electrolyte balance, the liver plays a central role in metabolism and detoxification, and the lungs are crucial for respiration and gas exchange. Though these organs can produce certain hormones or substances with hormonal effects, they do not function as integral components of the endocrine system like the pituitary gland.